1. Field of the Invention
This invention relates to a method of generating an enlarged image signal using a field memory.
2. Description of the Prior Art
A conventional process for electronically enlarging an image signal using a memory is executed as follows. First, image signals for one frame on an input screen are written into a memory. A desired area of the written image signal to be enlarged is designated and read. A process for enlarging the read image signal is executed and the processed image signal is delivered to a monitor so that a corresponding image is displayed.
A field memory simplifies the control since the number of control signals used is small. Accordingly, the field memory is used as the above-described memory in the image signal enlarging process. However, the use of the field memory reveals the following disadvantages. In the field memory, a write address serving as a write location and a read address serving as a read location are sequentially incremented from a start address by a write-in clock (WCLK) and a read-out clock (RCLK) respectively. The write address and the read address can be returned to the start address by respective reset signals. However, a writing operation and a reading operation following the write and read addresses respectively can be executed only by sequential addresses.
Accordingly, when the image signals of one frame written into the field memory is read out so that the image signal of an enlarged area is extracted, the image signal other than the enlarged area needs to be discharged at high speeds. Thus, it is not easy to extract only the image signal of the area to be enlarged during the processing of dynamic images.